Graphene is a two dimensional arrangement of sp2-bonded carbon atoms. Usually, graphene exists as individual sheets. Even so, in graphite, π bonds between graphene sheets may form sheet-to-sheet bonding. Carbon nanotubes might be considered to be graphene sheets rolled into tube shapes. Carbon nanotubes have many unique and desirable characteristics for making high-performance electronic devices. Conceptually, the direction in which a graphene sheet rolls to form a carbon nanotube controls the chirality, giving the nanotube metallic, semi-conducting, or insulating characteristics. Electrons exhibit very high mobility and zero effective mass in nanotubes and, by extension, graphene sheets.
Some have accomplished formation of graphene sheets by mechanical exfoliation, or peeling, with expected complications in control of graphene positioning and adhesion to substrates. Some have proposed graphene formed by epitaxial deposition methods on silicon substrates as potentially suitable for high performance CMOS devices. However, epitaxial deposition of graphene is expected to be complex and might not yield sufficiently low defect densities. As a result, a need exists in the art for graphene formation methods more conducive to incorporating graphene into electronic devices.